Metallocenyl Phthalocyanine Compounds and Use Thereof

ABSTRACT

This invention relates to a novel metallocenyl phthalocyanine compound represented by the following general formula (I), in which at least one of the four benzene rings of phthalocyanine is connected with the organometallic complex group through a linker having one carbon atom. This invention also relates to the use of the phthalocyanine compounds in optical recording media.  
                 
wherein all symbols are defined in the specification.

TECHNICAL FIELD

This invention relates to novel metallocenyl phthalocyanine compoundsand derivatives thereof, and their use for the recording layers ofoptical recording media.

BACKGROUND OF THE INVENTION

With the rapid growth of our digital world, the technology for opticalstorage is being highly developed. The advantages of an optical mediumdisk are that data are easily recorded on such a medium, it is suitablefor enduring storage, and it has a modest cost. This recording datamedium is now becoming an accepted way to store information because ofits large storage capacity.

The field of this invention is directed to dyes used in the recordinglayer on a writable optical disk, because such dyes exhibit variedoptical properties upon irradiation. There are optical disks of severalkinds as follows: (I) Write Once, Read Many (WORM); (2) Read Only Memory(ROM); (3) Erasable Direct Read after Write (EDRW). In a disk of WORMtype, the recording material uses mainly dyes capable of absorbing lightin the near infrared region (NIR region), as described by M. Emmelius inAngewandte Chemie, No. 11, pages 1475-1502 (1989). It is based primarilyon the principle that laser irradiation of the dyes can produce thechanges in absorption necessary to record information in digital form insuch recording materials by means of physical (for example, bysublimation or diffusion) or chemical (for example, photochromy,isomerization or thermal decomposition of the dye) changes.

The optical recording medium disks for storage information in the marketare DVD-R as 8x˜16x, and CD-R as 32x˜52x. When a CD-R operates at alarge writing speed, the jitter value at short pits or lands can bedecreased with a relatively thin recording layer, but this thin layerrequires an increased writing power at a given writing speed, which onceagain limits the maximum achievable writing speed at a given laserpoint.

Recording materials are, however, unable to meet fully the increasedrequirements at great writing speeds. In particular, it is found thatthe optimum thickness of the recording layer varies depending on therange of writing speed. Whereas, at a small writing speed, anunsatisfactorily small contrast is generally the critical parameter thatcan be improved with a relative thick layer, at a large writing speed,the critical parameter is generally excessive jitter at short pits orlands (in particular L3T), which can be decreased with a relatively thinrecording layer. A thin layer requires, undesirably, an increasedwriting power at a given writing speed, which once again limits themaximum achievable writing speed at a given laser point.

The recording layer to be used must meet demanding requirements such asa large index of refraction and small absorption at the laserwavelength, a large contrast of the written pits, a uniformity of thepit with varied pit length, great light stability in daylight and underweak laser radiation (reading) while concurrently maintaining a greatsensitivity under intense laser radiation (writing), great long-termstability, small noise, high resolution and—a particularly importantaspect—a minute systematic and random deviation (‘jitter’) of pit lengthfrom a prescribed value at an optimum writing power.

Among various dyes used in the optical recording medium, phthalocyanineis a widely used material and remains the most important. Phthalocyainehas the advantages of excellent light and environmental stability. Thedisadvantages of phthalocyanine are (1) lack of light sensitivity, (2)poor solubility, (3) a high temperature required for recording, and (4)a small reflectivity. For these reasons other substituents must beincorporated into the phthalocyanine molecular structure. U.S. Pat. Nos.5,270,463 and 5,280,114 disclosed phthalocyanines involving bulkysubstituents, for example, a branched alkoxy group and halide at thesame time to decrease the temperature needed for recording and toincrease the solubility of the phthalocyanine dye. Although thephthalocyanines disclosed in this patent can decrease the decompositiontemperature, and possess excellent writing decomposability, increasedsolubility in the solvent and increased reflectivity, thesephthalocyanines also result in an increased Block Error Rate (BLER) whena greater writing speed is required; thus its writing property is alsodiminished.

EP-A 600427 disclosed a dye for a recording layer in an opticalrecording medium that is based on phthalocyanines with a few additives,for example, a combustion aid such as ferrocenyl derivatives, or anantiknocking agent to improve the heat decomposability and recordingproperty, but it is still unsatisfactory for recycling because of thesolubility difference between the phthalocyanines and the additives.

WO 97/23354 disclosed a method to solve the problem of the disparatesolubility by binding the metallocenyl and the phthalocyanines, but itsrecording property is still unsatisfactory.

WO 00/09522, WO 03/068865 and WO 02/083796 disclosed binding themetallocenyl and the phthalocyanines via a bridging unit E, where E iscomposed of a chain of at least two atoms or atom groups selected fromthe group consisting of —CH₂—, —C(C═O)—, —CH(C₁₋₄ alkyl)-, —C(C₁₋₄alkyl)₂-, —NH—, —S—, and —O—, to produce metallocenyl phthalocyaninesthat are capable of use in recording layers of recording media withhigh-speed writing.

In summary from the above-mentioned prior arts, it is generallyconsidered that metallocenyl phthalocyanines prepared by bindingphthalocyanines and metallocene together through use of an atomic groupare beneficial for use in a recording layer of a high-speed rewritablerecording medium and can resolve the problems encountered in therecovering/recycling process. Moreover, their solubility in solventscommonly used in this field is increased and their decomposability andrewriting stability are greatly improved.

Currently, only altering the specificity of the phthalocyaninestructures themselves can not achieve a great sensitivity ratio (C/N,carrier to noise), optimal recording power and recording properties(such as small jitter) required in recording media. Also, from relevantpapers and patent publications, it is pointed out that the compoundobtained on bonding phthalocyanines and metallocene can greatly improveits sensitivity and recording properties when it is used as a dye in arecording layer for recording media, but the preparation of metallocenylphthalocyanines requires multiple steps so that its cost of productionbecomes increased. Moreover, phthalocyanine compounds are slightlysoluble in non-polar solvents commonly used in preparing recordingmaterial; thus when the phthalocyanine compounds are used in a solutionto prepare the recording layer, the phthalocyanine compounds aggregateslowly and in turn precipitate after use for a period of time. Aphthalocyanine compound having resolved the above problems and a simpleprocess to prepare the same are therefore needed.

SUMMARY OF THE INVENTION

Under the above circumstances, the present inventors have conductedinvestigation of the structure of phthalocyanine compounds and theirsynthesis and found that novel metallocenyl phthalocyaninecompounds/mixtures obtained on connecting phthalocyanine withmetallocene through a linker containing one carbon atom through aFriedel-Crafts reaction exhibit excellent recording sensitivity andsmall jitter, and are thus suitable for use in high-speed rewritablerecording media. Moreover, these novel metallocenyl phthalocyaninecompounds/mixtures can be prepared with a simple process so that theirproduction cost can be moderate. Especially, because the linkerconnecting phthalocyanine with metallocene contains only one carbonatom, the solubility in non-polar solvents is satisfactory, so resolvingthe problems of aggregation and precipitation.

The invention relates to metallocenyl phthalocyanine compounds and theirmixtures that have satisfactory solubility (>6 mass %) in solvents, thatcan be prepared with a simple process, and that are suitable for use inrecording layers of optical recording media.

In one aspect, this invention relates to novel metallocenylphthalocyanine compounds represented with formula (I) that are suitablefor use in high-speed rewritable recording media:

wherein,

M₁ represents two hydrogen atoms, a divalent metal, a trivalent metalhaving one liganid, or a tetravalent metal having two ligands;

Y₁, Y₂, Y₃, Y₄ each independently represents groups of —O—R₁, —S—R₁, or—NR₁R₂;

R₁ and R₂ each independently represents a hydrogen atom; a C₁-C₁₀straight-chain, branched, or cyclic alkyl; a C₂-C₁₀ straight-chain,branched, or cyclic alkenyl; or a C₂-C₁₀ straight-chain, branched, orcyclic alkynyl;

Z represents a group of the following formula:

in which R₃ and R₄ each independently represents a hydrogen atom, aC₁-C₄ alkyl, or a C₂-C₄ alkenyl;

R₅ and R₆ each independently represents a hydrogen atom, a halogen atom,a nitro group, a C₁-C₄ alkyl, a C₁-C₄ alkoxy, a C₁-C₄ alkylamino, adi(C₁-C₄alkyl)amino, or a diarylphosphine group;

M₂ is selected from an atom consisting of Fe(II), Co(II) and Ni(II);

wherein l, m, n, o each independently represents 0, 1 or 2, and l+m+n+ois between 1 and 8.

The metallocenyl phthalocyanine compounds of this invention (sometimesreferred to “the present metallocenyl phthalocyanine compounds”hereinafter) can be in a mixture without isolation. Thus the compoundrepresented by the above formula (I) includes those in a purified formand in a mixture form without isolation.

This invention also relates to a process for preparing the presentmetallocenyl phthalocyanine compounds and to their use in a recordinglayer of an optical recording medium.

DETAILED DESCRIPTION

This invention relates to novel compounds of formula (I),

wherein

M₁ represents two hydrogen atoms, a divalent metal, a trivalent metalhaving one ligand, or a tetravalent metal having two ligands;

Y₁, Y₂, Y₃, Y₄ each independently represents a group —O—R₁, —S—R₁, or—NR₁R₂;

R₁ and R₂ each independently represents a hydrogen atom; a C₂-C₁₀straight-chain, branched, or cyclic alkyl; a C₂-C₁₀ straight-chain,branched, or cyclic alkenyl; or a C₂-C₁₀ straight-chain, branched, orcyclic alkynyl;

Z represents a group of formula:

in which R₃ and R₄ each independently represents a hydrogen atom, aC₁-C₄ alkyl, or a C₂-C₄ alkenyl;

R₅ and R₆ each independently represents a hydrogen atom, a halogen atom,a nitro group, a C₁-C₄ alkyl, a C₁-C₄ alkoxy, a C₁-C₄ alkylamino, adi(C₁-C₄alkyl)amino, or a diarylphosphine group;

M₂ is selected from atoms consisting of Fe(II), Co(II), and Ni(II);

wherein l, m, n, o each independently represents 0, 1 or 2, and l+m+n+ois between 1 and 8.

In the metallocenyl phthalocyanine compounds represented by formulae(I), when M₁ represents two hydrogen atoms, it signifies that these twohydrogen atoms each bond to the N atom in the N-containing heterocyclicring.

The divalent metals represented by M₁ are, for example, Cu (II), Zn(II), Fe (II), Ni (II), Ru (II), Mn (II), Pd (II), Pb (IT), or Co (II).

The trivalent metals represented by Ml are the metals with onecoordination site, for example, Al—Cl, Al—Br, Al—I, Ga—Cl, Ga—Br, Ga—I,In—Cl, In—Br, In—I, Ti—Cl, Ti—Br, Ti—I, Fe—Cl, Ru—Cl, Mr(OH), or Al(OH).

The tetravalent metals represented by M₁ are metals with twocoordination sites, for example, CrCl₂, SiCl₂, SiBr₂, SiCl₂, ZrCl₂,GeCl₂, GeBr₂, Gel₂, SnCl₂, SnBr₂, SnI₂, TiCl₂, TiBr₂, Til₂, Si(OH)₂,Ge(OH)₂, Zr(OH)₂, Mn(OH)₂, or Sn(OH)₂.

The saturated, branched or cyclic kind of C₁-C₁₀ unsubstituted orsubstituted alkyl represented by R₁ and R₂ is, for example, methyl,ethyl, propyl, isopropyl, n-butyl, n-pentyl, n-hexyl, isohexyl, heptyl,octyl, nonanyl, decanyl, isobutyl, sec-butyl, tert-butyl, isopentyl,neopentyl, 1,2-dimethylpropyl, 1,1-dimethylbutyl, 7,2-dimethylbutyl,2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,3-dimethylbutyl,1-isopropylpropyl, 1,2-dimethylbutyl, 2-methylhexyl, 3-methylhexyl,4-methylhexyl, 5-methylhexyl, 1,2-dimethylpentyl, 1,3-dimethylpentyl,1,4-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl,2,3-dimethyl-2-pentyl, 2,4-dimethyl-2-pentyl, 3,3-dimethyl-2-pentyl,3,4-dimethyl-2-pentyl, 4,4-dimethyl-2-pentyl, 2,2-dimethyl-3-pentyl,2,3-dimethyl-3-pentyl, 2,4-dimethyl-3-pentyl, 2-methylheptyl,3-methylheptyl, 4-methylheptyl, 2,2-dimethylheptyl, 2,3-dimethylhexyl,2,4-dimethylhexyl, 2,5-dimtheylhexyl, 3,5-dimethylhexyl,2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,4-trimethyl-2-pentyl,2,4,4-trimethyl-2-pentyl, 2,2,4-trimethyl-3-pentyl,2,3,4-trimethyl-3-pentyl, 2,2-dimethylheptyl, 2,4-dimethylheptyl,2,5-dimethylheptyl, 3,5-dimethylheptyl, 2,6-dimethyl-4-heptyl,2-methyl-1-isopropylpropyl, 1-ethyl-3-methylbutyl,3-methyl-1-isopropylbutyl, 2-methyl-1-isopropylbutyl,1-sec-butyl-2-methylpropyl, 2-ethylhexyl, cyclopentyl, cyclohexyl,2-methylcyclopentyl, 1-methylcyclopentyl, cycloheptyl,1-methylcyclohexyl, 2-methylhexyl, 4-methylcyclohexyl,2,4-dimethylcyclopentyl, 2,6-dimethylcyclopentyl, 2-ethylcyclopentyl,cyclooctyl, 2-methylcycloheptyl, cyclononanyl and the like.

R₁ and R₂ can each be, independently of one another, a C₁₋₁₀ alkyl orcycloalkyl group substituted with halogen, for example, 2-chloroethyl,3-bromopropyl, 2,2,3,3-tetrafluoropropyl, 1, 1,1,3,3,3-hexafluoro-2-propyl, 2-chlorocyclopentyl, 2-chlorocycloheptyland the like. R₁ and R₂ can each be, independently of one another, anunsaturated C₁-C₁₀ alkyl substituted with an alkoxy, for example,2-methoxylethyl, 2-ethoxyl ethyl, 2-butoxyl ethyl, 1-ethoxy-2-propyl,2-methoxyl propyl, 3-methoxylbutyl and the like; or an unsaturatedC₁-C₁₀ alkyl substituted with di-alkyl amino group, for example,2-dimethylaminoethyl, 2-diethylaminoethyl, 2-dipropylaminoethyl,2-dibutylaminoethyl, 2-diethylaminopropyl and the like.

R₁ and R₂ can each be a C₂-C₁₀ straight-chain, branched or cyclic chainalkenyl, for instance, ethenyl, propenyl, isopropenyl, n-butenyl,isobutenyl, sec-butenyl, 1-methylpropenyl, n-pentenyl, neopentenyl,tert-pentenyl, 2-methylbutenyl, 3-methylbutenyl, 2-methylpentenyl,3-methylpentenyl, 4-methylpentenyl, 2,3-dimethylbutenyl, n-hexenyl,heptenyl, 2-methylhexenyl, 3-methylhexenyl, 4-methylhexenyl,5-methylhexenyl, 2,4-dimethylpentenyl, octenyl, 2-methylheptenyl,6-methylheptenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl,cyclooctenyl, cyclononanenyl, cyclodecanenyl and the like.

R₁ and R₂ can each be a C₂-C₁₀ straight-chain, branched or cyclic chainalkynyl, for instance, ethynyl, propynyl, isopropynyl, n-butynyl,isobutynyl, sec-butnyl, tert-butynyl, n-pentynyl, isopentynyl,neopentynyl, 1-methylbutynyl, 2-methylbutynyl, 1,1-dimethylpropynyl,1,1-dimethylbutynyl, 2,2-dimethylbutynyl, n-hexynyl, isohexynyl,heptynyl, octynyl and the like.

Z is a group of formula

wherein M₂ is a divalent metal, for example, Fe (II), Co (II), and Ni(II); and

R₃, R₄, R₅, and R₆ can each be a C₁-C₄ straight-chain alkyl, forexample, methyl, ethyl, n-propyl, n-butyl, and the like, or a branchedalkyl, for example, isopropyl, sec-butyl, tert-butyl, and the like.

R₃ and R₄ can each be a C₂-C₄ straight-chain alkenyl for example,ethenyl, n-propenyl, n-butenyl, and the like, or a branched alkenyl, forexample, isopropenyl, isobutenyl, and the like.

The halogen represented by R₅ and R₆ is, for example, fluoro, chloro,bromo and iodo.

The C₁-C₄ alkoxy group represented by R₅ and R₆ is, for example,methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy,1-methoxypropyl, 2-methoxypropyl, 3-methoxypropyl, and the like.

The C₁-C₄ alkylamino or di-(C₁-C₄) alkylamio group represented by R₅ andR₁ is, for example, methylamino, ethylamino, propylamino,isopropylamino, n-butylamino, sec-butylamino, isobutylamino,tert-butylamino, dimethylamino, diethylamino, dipropylamino,di-iso-propylamino, dibutylamino, di-sec-butylamino, di-iso-butylamino,di-tert-butylamino, and the like.

The diarylphosphine group represented by R₅ and R₆ is, for example,diphenylphosphine and substituted diphenylphosphines.

To illustrate directly the present invention, the carbons on the benzenerings in the metallocenyl phthalocyanine compounds represented byformula (I) are numbered as follows:

In formula (I), Y₁, Y₂, Y₃ and Y₄ can each be a substituent connected tothe benzene rings each being optionally substituted at any one ofpositions 1-16 available; Y₁, Y₂, Y₃ and Y₄ can be the same substituentor differ from each other.

Preferably, Y₁ is at position 1 or 4 of the benzene ring, Y₂ is atposition 5 or 8, Y₃ is at position 9 or 12, and Y₄ is at position 13 or16; for example, Y₁ is at position 1, Y₂ is at position 5, Y₃ is atposition 9, and Y₄ is at position 13.

Moreover, substituent Z can be at any carbon at which no substituent Y₁,Y₂, Y₃ and Y₄ is present. The symbols l, m, n and o represent the numberof the substituents of Z, each being 0, 1 or 2, and (l+m+n+o) is between1 and 8.

The preferred embodiment of the present compound is the compound whereinY₁, Y₂, Y₃ and Y₄ are —ORE, i.e. the compound represented by formula(II),

wherein

M₁ represents Cu (II) or Pd (II),

Z′ is a group of the following formula:

wherein R₁, R₅, R₆ and M₂ are the same as those defined in formula (I),each 1′, m′, n′ and o′ is independently 0, 1 or 2, and (l′+m′+n′+o′) isbetween 1 and 4.

The particularly preferred embodiment of the present compound is thecompound wherein M₁ is Cu(II), and —OR₁ is 2,4-dimethyl-3-pentoxyl, i.e.the compound represented by formula (III),

wherein Z″ is a group of the following formula:

each l′, m′, n′ and o′ is independently 0, 1 or 2, and (l′+m′+n′+o′) isbetween 1 and 4.

In the present invention, the metallocenyl phthalocyanines representedby formula (I) can exist in a mixture without isolation.

This invention also relates to a recording layer of an optical recordingmedium, which comprises the metallocenyl phthalocyanine single or in amixture, of formula (I) and optionally anotherphthalocyanine/phthalocyanine mixture, such as the phthalocyaninerepresented by formula (IV),

wherein M₁, Y₁, Y₂, Y₃, and Y₄ are defined as the formula (I).

The recording layers comprise

-   -   (a) 70-100% of the metallocenyl phthalocyanine or a mixture        represented by formula (I); and

(b) 0-30% of the other phthalocyanine or mixture represented by formula(I) based on 100% by mass of the metallocenyl phthalocyaninesrepresented by formula (I) and the other optional phthalocyaninesrepresented by formula (IV).

In the recording layer of an optical recording medium of the presentinvention, the preferred embodiment of metallocenyl phthalocyaninecompound is a compound represented by formula (II),

Z′ is a group of the following formula:

wherein M₁, M₂, R₁, R₅, R₆, l′, m′, n′ and o′ are defined as above.

In this case, the recording layers comprise

(a) 70-100% of the metallocenyl phthalocyanine or a mixture representedby formula (II); and

(b) 0-30% of the other phthalocyanine or mixture represented by formula(IV), based on 100% by mass of the metallocenyl phthalocyaninesrepresented by formula (II) and the other optional phthalocyaninesrepresented by formula (IV).

In the recording layer of an optical recording medium of the presentinvention, the particularly preferred embodiment of metallocenylphthalocyanine compound is a compound represented by formula (III),

wherein Z″ is a group of formula

and l′, m′ n′ and o′ are defined as above.

In this case, the recording layers comprise

(a) 70-100% of the metallocenyl phthalocyanine or a mixture representedby formula (III); and

(b) 0-30% of the other phthalocyanine or mixture represented by formula(IV), based on 100% by mass of the metallocenyl phthalocyaninesrepresented by formula (III) and the other optional phthalocyaninesrepresented by formula (IV).

This invention also relates to a novel process for preparing thecompound represented by formula (I), which comprises subjecting ametallocenyl complex and a phthalocyanine to a Friedel-Crafts reaction.

The metallocellyl complex used in the present process is represented bythe formula (V).

wherein L is a leaving group, for example, —Cl, —Br, —I, —OTs, —OMs,OTf, —OAc, —OPiv, —OBz, —OH,

and the like; preferably —Cl, —Br, —I, —OTs, —OH; and

R₃, R₄, R₅R₆, M₂ are defined as in formula (I).

In the present process, the preferred metallocenyl complex is thatrepresented by formula (VI),

wherein L′ is a leaving group, for example, —Cl, —Br, —I, —OTs, —OH andthe like; and R₅, R₆, M₂ are defined as in formula (I).

In the present process, the particularly preferred metallocenyl complexis that represented by formula (VII),

wherein R₅ and R₆ are each a hydrogen atom or C₁-C₄ alkyl, preferably ahydrogen atom.

J. Am. Chem. Soc. 1966, 88, 3442-3444 has described that α-ferrocenylcarbonium ion exhibits—carbocation stabilization. Thus the compoundrepresented by formula (V) is easily shifted to form the followingintermediate under an acidic catalysis, which intermediate is similar tothe α-ferrocenyl carbonium ion:

The process for preparing the metallocenyl phthalocyanines of thepresent invention comprises alkylating a phthalocyanine of the followingformula (IV):

wherein M₁, Y₁, Y₂, Y₃, Y₄ are defined as above, with a metallocenecompound of formula (V) in the presence of an acidic catalyst:

wherein R₃, R₄, R₅, R₆, M₂, and L are defined as above, to afford thepresent metallocenyl phthalocyanine.

In the above reaction, the metallocene compound of formula (V) firstforms an acidic ion pair consisting of an α-ferrocenyl carbonium ion andthe L anion, and then it is reacted and bonded with the phthalocyanineof formula (IV) through a group containing one carbon in suitablereaction conditions to fom the present metallocenyl phthalocyanine.

The ratio of metallocene (formula (V)) to phthalocyanine (formula (IV))for the alkylation reaction is between 8:1 and 0.5:1, preferably between4:1 and 1:1.

The reaction is conducted in aprotic solvents, for example,dichloromethane, dichloroethane, chloroform, chlorobenzene, toluene,xylene, acetonitrile, trimethylbenzene, tetrahydrofuran, or ethyleneglycol dimethyl ether, and the like. The mass ratio of solvents andphthalocyanine (IV) is between 2:1 and 40:1, preferably between 6:1 and12:1.

The reaction is facilitated by acidic catalysts, for example, inorganicacids or organic acids. The inorganic acids can be, for example, H₂SO₄,HClO₄, H₃PO₄, HCl, HBr and the like. The organic acids can be, forexample, toluenesulfonic acid, benzenesulfonic acid,trifluoromethanesulfonic acid, trifluoroacetic acid and the like. TheLewis acids can be, for example, AlC₃, ZnCl₂, BF₃ and the like.

The amounts of the catalyst depend on the property of the catalyst, andthe molar ratio of the catalyst to the phthalocyanine (IV) is from 0.1to 2.0, preferably from 0.2 to 1.0.

The reaction temperature depends on the solvent and catalyst, and thetemperature is generally from 20 to 120° C., preferably from 50 to 90°C.

The duration of reaction depends on the reaction temperature, solventused and amounts of catalyst. It is generally from 2 to 24 h, preferablyfrom 12 to 16 h.

Metallocenyl phthalocyanine of formula (II) can be synthesized fromcompound (VIII) and compound (VI) by the Friedel-Crafts reaction in thepresence of an acidic catalyst.

M₁ and R₁ are defined the same as in formula (II).

The metallocenyl phthalocyanine of the present invention is prepared onconnecting metallocene (formula (V)) and phthalocyanine (formula (IV))through a linker having one carbon atom under the acid catalyst. Thenovel synthetic strategy involves a linker having one carbon atom, and ashort route for the synthesis. The present metallocenyl phthalocyaninesexhibit an excellent sensitivity and excellent optical recordingproperties when they are used in the recording layers of opticalrecording media.

In the present invention, the recording layer containing the presentmetallocenyl phthalocyaninies and/or mixtures thereof shows λmax at 690nm˜780 n. As the recording layer is generally applied from a solution,for example by spin coating, the dyes should be readily soluble incustomary solvents, for example as described in EP-A 511 598(independently of the distinction between polar and non-polar solventsmade therein).

Examples of coating methods for optical recoding media are spin coating,sputtering deposition, vapor deposition and dip coating; among them,spin coating is preferable because of the ease of control of the filmthickness of the land/groove of the recording layer. For the spincoating, a preferable solvent is one that is unreactive with thesubstrate.

The advantages of the present invention are: (1) metallocenylphthalocyanines and their derivatives have improved solubility insolvents of low polarity, thus avoiding use of highly polar volatilesolvents, such as acetone, dichloroethane and dimethylformamide. Inaddition, the solvents should be chosen from non-polar solvents that donot damage the substrate, for example, selected from alicyclichydrocarbons such as cyclohexane, methylcyclohexane,dimethylcyclohexane, isopropylcyclohexane, cyclooctane; ethers such asdiethylether, dipropylether, diisopropylether, di-n-butylether,di-iso-butylether, di-n-pentylether; alcohols such as isopropanol,isobutanol, or cyclopentanol.

Furthermore, other cosolvents may be used in preparing the solutioncontaining the present metallocenyl phthalocyanines, for example,toluene, xylene, trimethylbenzene, methyl isobutyl ketone,diisobutylketone or 2,6-dimethyl-4-heptanone and the like.

Some solvents have been suggested for use in preparing the recordinglayers, for example, DBE (di-n-butylether), ECH (ethylcyclohexane) orDMCH (dimethylcyclohexane). The suggested cosolvent is1,2,4-trimethylbenzene. Conventionally, in preparing the solution forcoating the recording layer, the phthalocyanines are typically in aconcentration 2-3% (mass/v). However, the present metallocenylphthalocyanes and/or derivatives thereof can be used in a concentrationmore than 6% (mass/v) because of their excellent solubility in theselected solvents.

The invention is further described in the following examples. It shouldbe understood that these examples are for illustrative purposes only andare not to be construed as limiting this invention in any manner.

EXAMPLES Example 1

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in 1,2-dichloroethane (300 mL) and stirred for 0.5 h in adry flask. Chloromethylferrocene (FcCH₂Cl, 12.2 g) (FcCH₂Cl was preparedby the known method described in J. Am. Chem. Sodc 1966, 88, 3442-3444)was added, and subsequently aluminium chloride (1.56 g) was crushed andadded promptly. The mixture was stirred for 10 min, warmed up to 80 ACfor another 4 h and then cooled to room temperature.

The mixture aforementioned was poured into a solution mixed with ice(180 g) and water (180 mL) in a beaker (1 L), and stirred; thetemperature was controlled about 10° C. for 1 h. The solution was pouredinto a separatory funnel and extracted with water (300 mL) twice. Theorganic layers were collected, concentrated to approximately 70 g, andpoured into a methanol (900 mL) solution with stirring by a mechanicalagitator at a temperature about 10° C. The precipitate was formed andfiltered. The filtered cake was washed with methanol (30 mL) three timesto give a green residue. The green residue was purified on achromatographic column (silica gel 60H, Merck, toluene:hexanes=1:4) togive a blue-green solid of a mixture (substance 1) (21.5 g).

The mixture (substance 1) has the following properties:

FAB MS (rnz): 1230(CPc-CH₂Fc), 1428(Cuc-(CH₂Fc)₂), 1626(CuPc-(CH₂Fc)₃)

UV/VIS: λ max=718 nm (NMP), max=1.79×10⁵ mL/g·cm

IR(KBr): 3091, 2961, 2873, 1587, 1486, 1335, 1266, 1089, 1038, 746 cm⁻¹.

Example 2

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in 1,2-dichloroethane (300 mL) and stirred for 0.5 h in ad flask. Chloromethylferrocene (FcCH₂Cl, 12.2 g) was added, and thensulfuric acid (98%, 0.86 g) was slowly added. The mixture was stirredfor 10 min, warmed to 90° C. for another 3 h, and then cooled to roomtemperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (60 g) and water(300 mL). The mixture was stirred and the temperature was controlled at10˜15° C. for 0.5 h. The solution was poured into a separatory funnel,and extracted with water (300 mL) twice. The organic layers werecollected, concentrated to approximately 70 g, and poured into amethanol (900 mL) solution with stirring by a mechanical agitator at atemperature about 10° C. A precipitate was formed and filtered. Thefiltered cake was washed with methanol (30 mL) three times to give agreen residue. The green residue was purified on a chromatographiccolumn (silica gel 60H, Merck, toluene:hexanes=1:4) to give a blue-greensolid of a mixture (19.7 g).

The mixture has the following properties:

FAB MS (m/z): 1230(CuPc-CH₂Fc), 1428(CuPc-(CH₂Fc)₂), 1626(CuPc-(CH₂Fc)₃)

UV/VIS: λ max=719 nm (MP), max=1.68×10⁵ mL/g·cm

IR (KBr): 3092, 2963, 2872, 1586, 1485, 1335, 1266, 1087, 1038, 745cm⁻¹.

Example 3

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in 1,2-dichloroethane (300 mL) in a dry flask and stirredfor 0.5 h. Chloromethylferrocene (FcCH₂Cl, 12.2 g) was added, andsubsequently aluminium chloride (2.33 g) was crushed and added promptly.The mixture was stirred for 10 min, warmed to 80° C. for another 6 h andthen cooled to room temperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (180 g) and water(180 mL). The mixture was stirred, and the temperature was controlled at10° C. for 1 h The solution was poured into a separatory funnel, andextracted with water (300 mL) twice. The organic layers were collected,concentrated to approximately 100 g, and poured into a methanol (900 mL)solution with stirring by a mechanical agitator with the temperaturecontrolled at 10° C. A precipitate was formed and filtered. The filteredcake was washed with methanol (30 mL) three times to give a greenresidue. The green residue was purified on a chromatograph column(silica gel 60H, Merck, toluene:hexanes=1:4) to give a blue-green solidof a mixture (substance 2) (24.9 g).

The mixture (substance 2) has the following properties:

FAB MS (m/z): 1230(CuPc-CH₂Fc), 1.428 (CuPc-(CH₂Fc)₂),1626(CuPc-(CH₂Fc)₃), 1824(CuPc-(C₁H₂c)₄), 2022(CuPc-(CH₂Fc)₅)

UV/VIS: λ max-722 nm (NMP), max=1.57×10⁵ mL/g·cm

IR (KBr): 3091, 2961, 2873, 1588, 1485, 1335, 1266, 1087, 1038, 745cm⁻¹.

Example 4

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in toluene (240 mL) and stirred for 0.5 h in a dry flask.Chloromethylferrocene (FcCH₂Cl, 12.2 g) was added, and subsequentlyaluminium chloride (1.56 g) was crushed and added promptly. The mixturewas stirred for 10 min, warmed to 70° C. for another 5 h and then cooledto room temperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (120 g) and water(240 mL). The mixture was stirred and the temperature was controlled at10° C. for 1 h. The solution was poured into a separatory funnel, andextracted with water (300 mL) twice. The organic layers were collected,concentrated to approximately 80 g, and poured into a methanol (1000n-L) solution with stirring with a mechanical agitator and at acontrolled temperature 10° C. A precipitate was formed and filtered. Thefiltered cake was washed with methanol (30 mL) three times to give agreen residue. The green residue was purified on a chromatographiccolumn (silica gel 60H, Merck, toluene:hexanes=1:4) to give a blue-greensolid of a mixture (substance 3) (18.5 g).

The mixture (substance 3) has the following properties:

FAB MS (m/z): 1230(CuPc-CH₂Fc), 1428(CuPc-(CH₂c)₂), 1626(CuPc-(CH₂Fc)₃),1824(CuPc-(CH₂Fc)₄).

UV/VIS: λ max=719 nm (NMP), max=1.72×10⁵ mL/g·cm

IR (KBr): 3091, 2963, 2872, 1587, 1486, 1335, 1266, 1088, 1038, 747cm⁻¹.

Example 5

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in 1,2-dichloroethane (300 mL) in a dry flask and stirredfor 0.5 h. Ferrocenemethanol (FcCH₂OH, 12.6 g) was added and thentrifluoromethane-sulfonic anhydrous (11.1 g) was slowly added. Themixture was stirred for 30 min. Subsequently, 98% sulfuric acid (1.71 g)was added and stirred for 10 min at room temperature. The mixture waswarmed to 90° C. for another 3 h and then cooled to room temperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (60 g) and water(300 mL). The mixture was stirred and the temperature was controlled at10-15° C. for 0.5 h. The solution was poured into a separatory funnel,and extracted with water (300 mL) twice. The organic layers werecollected, concentrated to approximately 70 g, and poured into amethanol (900 mL) solution with stirring by a mechanical agitator andwith the temperature controlled at 10° C. A precipitate was formed andfiltered. The filtered cake was washed with methanol (30 mL) three timesto give a green residue. The green residue was purified on achromatographic column (silica gel 60H, Merck, toluene:hexanes 1:4) togive a blue-green solid of a mixture (19.7 The mixture has the followingproperties:

FAB, MS (m/z): 1230(CuPc-CH₂Fc), 1428(CuPc-(CH₂FC)₂),1626(Cuc-(CH₂Fc)₃).

UV/VIS: λ max=717 NMP), max 1.73×10⁵ mL/g·cm.

IR (Kr): 3091, 2962, 2873, 1586, 1485, 1335, 1266, 1087, 1037, 744 cm⁻¹

Example 6

Tetra-(α-2,4-dimethyl-3-pentyloxy) copper phthalocyanine (CuPc, 30.0 g)was dissolved in 1,2-dichloroethane (300 mL) in a dry flask and stirredfor 0.5 h. 1-Ferrocenylethyl acetate (FcCH(CH₃)OAc, 15.8 g) was addedand subsequently aluminium chloride (194 g) was crushed and addedpromptly. The mixture was stirred for 10 min, warmed to 80° C. foranother 12 h and then cooled to room temperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (180 g) and water(180 mL). The mixture was stirred with the temperature controlled at10-15° C. for 1 h. The solution was poured into a separatory funnel, andextracted with water (300 mL) twice. The organic layers were collected,concentrated to approximately 80 g, and poured into a methanol (900 mL)solution with stirring by a mechanical agitator is and the temperaturecontrolled at 10° C. A precipitate was formed and filtered. The filteredcake was washed with methanol (30 mL) three times to give a greenresidue. The green residue was purified on a chromatographic column(silica gel 60H, Merck, toluene:hexanes=1:5) to give a blue-green solidof a mixture (3.1 g). The mixture has the following properties:

FAB MS (m/z): 1244(CuPc-CH₂(CH₃)Fc), 1456(CuPc-(CH₂(CH₃)Fc)₂).

UV/VIS: λ max=719 nm (N), max=1.92×10⁵ mL/g·cm

IR (KBr): 3086, 2960, 2924, 2870, 2855, 1584, 1488, 1337, 1265, 817cm⁻¹.

Example 7

Tetra-(α-2,4-dimethyl-3-pentyloxy)copper phthalocyanine (Cuc, 30.0 g)was dissolved in toluene (300) in a dry flask and stirred for 0.5 h.1-Ferrocenylethyl acetate (FcCH(CH₃)OAc, 15.8 g) was added, andsubsequently aluminium chloride (1.94 g) was crushed and added promptly.The mixture was stirred for 10 min, warmed to 100° C. for another 8 hand then cooled to room temperature.

The solution aforementioned was poured into a beaker equipped with amagnetic stirrer, and charged with a mixture of ice (180 g) and water(180 mL). The mixture was stirred with the temperature controlled at10˜15° C. for 1 h. The solution was poured into a separatory funnel, andextracted with water (300 mL) twice. The organic layers were collected,concentrated to approximately 80 g, and poured into a methanol (1 L)solution with stirring by a mechanical agitator and the temperaturecontrolled at 10° C. A precipitate was formed and filtered. The filteredcake was washed with methanol (30 mL) three times to give a greenresidue. The green residue was purified on a chromatographic column(silica gel 60H, Merck, toluene:hexanes=1:5) to give a blue-green solidof a mixture (2.6 g). The mixture has the following properties

FAB MS (m/z): 1244 (CuPc-CH₂(CH₃)Fc), 1456 (CuPc-(CH₂(CH₃)Fc)₂).

UV/VIS: λ max=719 nm (NMP), max=1.85×10⁵ mL/g·cm.

IR (KBr): 3086, 2961, 2924, 2870, 2855, 1585, 1488, 1338, 1265, 816 cm⁻¹

Example 8

Tetra-(α-2,4-dimethyl-3-pentyloxy)palladium phthalocyanine (PdPc, 100.0g) was dissolved in 1 L of 1,2-dichloroethane in a dry flask and stirredfor 0.5 h. Chloromethylferrocene (FcCH₂Cl, 44 g) was added andsubsequently aluminium chloride (7.5 g) was crushed and added promptly.The mixture was stirred for 10 mm, warmed to 80° C. for another 8 h andthen cooled to room temperature.

The mixture aforementioned was poured into a mixture of ice (400 g) andwater (800 mL) at 10° C. The solution was stirred for 1 h, poured into aseparatory funnel and extracted with water (800 mL) twice. The organiclayers were collected, concentrated to approximately 200 g, and pouredinto a methanol (2.4 L) solution with stirring by a mechanical agitatorand the temperature controlled at 10° C. A precipitate was formed andfiltered. The filtered cake was washed with methanol (120 mL) threetimes to give a green residue. The green residue was purified on achromatographic column (silica gel 60H, Merck, toluene:hexanes=1:6) togive a blue-green solid of a mixture (substance 4) (84 g).

The mixture (substance 4) has the following properties:

FAB MS (m/z): 1272(PdPc-CH₂Fc), 1470(PdPc-(CH₂Fc)₂),1668(PdPc-(CH₂Fc)₃).

UV/VIS: λ max=712 nm (NMP), max=1.54×10⁵/g·cm.

IR (KBr): 3090, 2962, 2874, 1598, 1499, 1325, 1264, 1107, 1042, 817, 746cm⁻¹.

Example 9

Tetra-(α-2,4-dimethyl-3-pentyloxy)palladium phthalocyanine (PdPc, 20.0g) was dissolved in 1,2-dichloroethane (200 mL) in a dry flask andstirred for 0.5 h. Chloromethylferrocene (FcCH₂Cl, 21.8 g) was added,and subsequently aluminium chloride (1.5 g) was crushed and addedpromptly. The mixture was stirred for 10 min, warmed to 80° C. foranother 8 h and then cooled to room temperature.

The mixture aforementioned was poured into a mixture of ice (100 g) andwater (200 mL) at a temperature 10° C. The solution was stirred for 1 h,poured into a separatory funnel and extracted with water (200 ml) twice.The organic layers were collected, concentrated to approximately 60 g,and poured into a methanol (500 mL) solution with stirring by amechanical agitator and the temperature controlled at 10° C. Aprecipitate was formed and filtered. The filtered cake was washed withmethanol (30 mL) three times to give a green residue. The green residuewas purified on a chromatographic column (silica gel 60H, Merck,toluene:hexanes=1:6) to give a green solid of a mixture (substance 5)(17.6 g).

The mixture (substance 5) has the following properties:

FAB MS (m/z): 1272(PdPc-CH₂Fc), 1470(PdPc-(CH₂Fc)₂),1668(PdPc-(CH₂Fc)₃), 1866(PdPc-(CH₂Fc)₄.

UV/VIS: λ max=716 nm (NMP), max 1.47×10⁵ L/g·cm.

IR (KBr): 3093, 2961, 2873, 1599, 1499, 1326, 1265, 1107, 1042, 812, 749cm⁻¹.

Example 10 CD-R Test

A solution of substance 1 (2.85 g) prepared as described in Example 1 ina mixture of DBE (Di-butyl ether) and 1,2,4-trimethyl benzene (94:3 bymass) that was filtered through a 0.1 μm filter (Teflon), was applied byspin coating onto a polycarbonate substrate (thickness 1.18 mm, diameter120 mm) with grooves 200 nm deep and 650 nm half width height with adistance 1.6 μm between two grooves. The disc was coated at a speed ofrotation 350 rpm for 5 s then at 3000 rpm for 10 s. The excess ofsolution was spun off on increasing the speed of rotation. All diskstested meet the specification in “Orange Book Part III:. CD-R W, Volume1, Version 2.0”. The absorption spectrum was measured over the visiblespectrum by means of a spectrophotometer, and the wavelength of themaximum absorbance was determined to be 0.52 μm. The uniformly appliedlayer was then dried at 80° C. in a convection oven for 20 min. A silverlayer (thickness 70 nm) was subsequently deposited on the resultingrecording layer in a vacuum-coating apparatus (Swivel, Balzers Co.). Aprotective layer (thickness 5 μm) of a UV-curing photopolymer (SD-394,manufactured by Dainippon Irk and Chemicals Incorporated (DIC)) was thenapplied thereto by spin coating and cured by irradiation with UV light(UVM-201 manufactured by Heng Ji Industrial Co., Taiwan) to form aprotective layer. The disk produced in this way was tested by means ofcommercial recorders (LTR-52327S, manufactured by Lite-on ItCorporation, 5232X manufactured by BenQ Corporation, and PX-W5224TAmanufactured by Plextor Co.) at a writing speed 48×. The measuredresults are shown in Table 1 below. TABLE 1 Recorder Type LTR-52327S5232X PX-W5224TA Highest Speed 48X 48X 48X Signal Length  3T 11T  3T 11T 3T 11T Pit Jitter 25 26  26 27  26 28  Land Jitter 28 29  26 28  27 26 Blur 0.3 0.1 0.5

Example 11 CD-R Test

Similar to example 10, 2.90 g of substance 2 prepared as described inExample 3 was used instead of substance 1. The measured results areshown in Table 2 below. TABLE 2 Recorder Type LTR-52327S 5232XPX-W5224TA Highest Speed 48X 48X 48X Signal Length  3T 11T  3T 11T  3T11T Pit Jitter 26 28  25 28  28 27  Land Jitter 25 28  28 27  26 27 Blur 0.5 0.4 0.2

Example 12 CD-R Test

Similar to example 10, substance 4 (2.94 g) prepared as described inExample 8 was used instead of substance 1. The measured results areshown in Table 3 below. TABLE 3 Recorder Type LTR-52327S 5232XPX-W5224TA Highest Speed 48X 48X 48X Signal Length  3T 11T  3T 11T  3T11T Pit Jitter 27 27  26 27  26 29  Land Jitter 26 28  27 28  28 28 Blur 0.5 0.4 0.2

It is to be understood that, although the invention has been describedin conjunction with the detailed description thereof, the foregoingdescription is intended to be illustrative and not to limit the scope ofthe invention, which is defined by the scope of the appended claims.Other aspects, advantages and modifications are within the scope of thefollowing claims.

1. A metallocenyl-phthalocyanine compound represented by formula (I):

wherein, M₁ represents two hydrogen atoms, a divalent metal, a trivalentmetal having one ligand, or a tetravalent metal having two ligands; Y₁,Y₂, Y₃, Y₄ each independently represents a group —O—R₁, —S—R₁, or—NR₁R₂; R₁ and R₂ each independently represents a hydrogen atom; aC₁-C₁₀ straight-chain, branched, or cyclic alkyl; a C₂-C₁₀straight-chain, branched, or cyclic alkenyl; or a C₂-C₁₀ straight,branched, or cyclic alkynyl; Z represents the group of formula

in which R₃ and R₄ each independently represents a hydrogen atom, aC₁-C₄ alkyl, or a C₂-C₄ alkenyl; R₅ and R each independently representsa hydrogen atom, a halogen atom, a nitro group, a C₁-C₄ alkyl, a C₁-C₄alkoxy, a C₁-C₄ alkylamino, a di(C₁-C₄alkyl)amino, or a diarylphosphinegroup in which the aryl is unsubstituted or substituted; M₂ is selectedfrom an atom consisting of Fe(II), Co(II), and Ni(II); wherein l, m, n,o each independently represents 0, 1 or 2, and l+m+n++o is between 1 and8.
 2. The compound according to claim 1, wherein M₁ is two hydrogenatoms, or a atom selected from Cu(II), Pd(II), Zn(II), Co(II), orNi(II).
 3. The compound according to claim 1, wherein M₁ is Cu(II) orPd(II).
 4. The compound according to claim 1, wherein Y₁, Y₂, Y₃ and Y₄each independently represents a group —O—R₁.
 5. The compound accordingto claim 1, wherein all Y₁, Y₂, Y₃ and Y₄ are 2,4-dimethyl-3-pentyloxy.6. The compound according to claim 1, wherein both R₃ and R₄ are ahydrogen atom; R₅ and R₆ are independently hydrogen, C₁-C₄ alkyl, orhalogen; and M₂ is Fe(II).
 7. An optical recording medium, whichcomprises a substrate, a recording layer and a reflecting or partiallyreflecting layer, wherein the recording layer comprises the compound ormixtures according to any one of claims 1 to
 6. 8. Ametallocenyl-phthalocyanine compound represented by formula (II):

wherein M₁ represents Cu(II) or Pd(II); R₁ represents a hydrogen atom, aC₁-C₁₀ straight-chain, branched, or cyclic alkyl; C₂-C₁₀ straight-chain,branched, or a cyclic alkenyl; or a C₂-C₁₀ straight-cha, branched, orcyclic alkynyl; Z′ represents a group of formula

in which R₅ and R₆ each independently represents a hydrogen atom, ahalogen atom, a nitro group, a C₁-C₄ alkyl, a C₁-C₄ alkoxy, a C₁-C₄alkylamino, a di(C₁-C₄alkyl)amino or a diarylphosphine group in whichthe aryl group is unsubstituted or substituted-M₂ is selected from anatom consisting of Fe(II), Co(II), and Ni(II); wherein l′, m′, n′, o′each independently represents 0, 1 or 2, and (l′+m′+n′+o′) is between 1and
 4. 9. The compound according to claim 8, wherein R₁ is2,4-dimethyl-3-pentyl.
 10. The compound according to claim 8, wherein R₅and R₆ are independently hydrogen, C₁-C₄ alkyl, halogen, and M₂ isFe(II).
 11. An optical recording medium, which comprises a substrate, arecording layer and a reflecting or partially reflecting layer, whereinthe recording layer comprises the compound or a mixture thereofaccording to any one of claims 8 to
 10. 12. A process for thepreparation of the metallocenyl phthalocyanine compound according toclaim 8, which comprise the reacting of a compound of formula (VIII) anda compound of formula (VI) via a Friedel-Crafts reaction in aproticsolvents and in the presence of an acidic catalyst at a temperaturebetween 20 and 120° C.:

wherein, M¹ represents Cu(I) or Pd(II); R₁ represents a hydrogen atom; aC₁-C₁₀ straight-chain, branched, or cyclic alkyl; a C₂-C₁₀straight-chain, branched, or cyclic alkenyl; or a C₂-C₁₀ straight-chain,branched, or cyclic alkynyl;

wherein L′ is a leaving group; R₅ and R₆ each independently represents ahydrogen atom, a halogen atom, a nitro group, a C₁-C₄ alkyl, a C₁-C₄alkoxy, a C₁-C₄ alkylamino, a di(C₁-C₄alkyl)amino, or a diarylphosphinegroup in which the aryl is unsubstituted or substituted; and M₂ isselected from an atom consisting of Fe(II), Co(II), and Ni(II).